An ink jet recording method is a printing method wherein droplets of an ink composition are ejected and deposited onto a recording medium such as paper. This method has a feature that an image having a high resolution and a high quality can be realized at a high speed with a relatively inexpensive apparatus. In general, the ink composition used in the ink jet recording method comprises water as a main component and, added thereto, a colorant and a wetting agent such as glycerin added for prevention of clogging and other purposes.
On the other hand, a new ink jet recording method has been recently proposed. The new method comprises applying a polyvalent metal salt solution onto a recording medium and then applying an ink composition containing a dye having at least one carboxyl group (e.g., Japanese Patent Laid-Open No. 202328/1993). According to this method, polyvalent metal ions combine with the dye to form an insoluble composite which can provide an image having water resistance and a high quality free from color bleeding.
Further, an ink jet recording method has been proposed wherein a color ink containing at least a surfactant or a penetrable solvent and a salt for imparting a penetrating property is used in combination with a black ink which cooperates with the salt to cause thickening or coagulation, thereby providing a high-quality color image having a high image density and free from color bleeding (Japanese Patent Laid-Open No. 106735/1994). More specifically, in this method, two liquids, i.e., a first liquid containing a salt and a second liquid of an ink composition, are printed to provide a good image.
Furthermore, other ink jet recording methods wherein two liquids are printed have been proposed, for example, in Japanese Patent Laid-Open No. 240557/1991 and No. 240558/1991.
In the above ink jet recording method wherein two liquids are printed, a need still exists for the following properties.
At the outset, an improvement in fixability of the colorant is required. In recent years, recycled papers have become used instead of wood free papers. For the recycled papers, the penetration of an ink is in general better than that for the wood free papers. For this reason, a high-quality image is formed on the wood free papers, whereas feathering or color bleeding is often created in the image formed on the recycled papers. Therefore, for recycled paper, the elimination of the feathering or color bleeding has been desired in the art.
Secondly, a reduction in uneven printing is required. The uneven printing refers to a variation in color density in the print derived from localization of a colorant on the paper. Although the uneven printing poses no significant problem in printing of letters of regular size, it is a serious problem in applications where figures, graphs and the like are printed.
Thirdly, broadening the range of usable colorants is required. Most of ink jet recording methods where two liquids are printed utilize a salting-out phenomenon between a metal ion and a carboxyl ion contained in the colorant so that the colorant should have a carboxyl group. Some dyes, however, contain a water-soluble group other than the carboxyl group. For example, some dyes may dissolve with a sulfonic group. A recording method which permits the use of dyes having a group other than a carboxyl group has been desired in the art.